Contact device for electrochemically deburring workpieces

ABSTRACT

In a device for the electrochemical deburring of workpieces which are connected as anodes and which includes a shaped tool electrode serving as cathode and an electrolyte between the anode and the cathode; the supply of the energy to the workpiece connected as anodes takes place by way of a contact electrode which, with the exception of its connection with the supply cable and the contact surface, is enclosed by insulating material; the contact body of the anode contact thereby consists of tungsten and is connected with the contact carrier consisting of a copperchrome alloy by friction welding.

United @tates Patent [1 1 [111 3,869,373

Schaciier 'et a1. 1 1 Mar. 4, 1975 v 1 1 CONTACT DEVICE FOR 3,654,122 4/1972 Williams 204/297 R ELECTROCHEMHCALLY DEBURRING 1' WOIAAHECES Primary Examiner-John H. Mack [75] Inventors: HansDieter S'chacher, Bernhausen; ASH-Slam weisstuch Reinhold Fischer, Burgstetten; Attorney, Agent, or FirmCraig & Antonelli Matthias Kunst, Hohenacker, all of Germany [73] Assignee: Daimler-Benz Aktiengesellschaft,

Stuttgart, Germany [57] ABSTRACT [22] Film: May 1973 In a device for the electrochemical deburring of work- 2 App] 359 41 pieces which are connected as anodes and which in cludes a shaped tool electrode serving as cathode and P an electrolyte between the anode and the cathode; the [30] j'oreign Apphcauo Prim-y Data supply of the energy to the workpiece connected as May 12 1972 Germany 2223152 anodes takes place by way of a contact electrode which, with the exception of its connection with the [52] U5- Ci 204/224 M, 20 /279 supply cable and the contact surface, is enclosed by [51] int. Cl B231) 1/02, C23b 5/68, Bolk 3/00 insulating material; the contact body of the anode 153] el Of a ch 0 297 224 contact thereby consists of tungsten and is connected 0 279 with the contact carrier consisting of a copper-chrome alloy by friction welding, 156] References Cited UNITED STATES PATENTS 7 Claims, 1 Drawing Figure 2,708,181 5/1955 Holmes et a1. 204/28 1 DEVE CE FUR ELEQTRUCll-IEMECALLY DEBURRHNE W OREQPHECES The present invention relates to a device for electrochemically deburring workpieces which are connected as anodes, with a shaped tool electrode serving as cathode and with electrolyte flowing between the anode and the cathode, whereby the supply of the energy to the workpiece takes place by way of an anode contact which, with the exception of the supply cable connection and the contact surface, is jacketed or encased with an insulating material. Material is removed locally limited at the workpiece by means of the formed electrode dependent on the flowing current and is conducted away by the electrolyte flow. In order to connect the workpiece during this operation with the current source, anode contacts are used which are connected with the power source andare pressed against the workpiece at places provided therefor and thus establish the electrical contact.

Anode contacts are in use at present which are coated or covered at their contact surface with a platinum layer. These anode contacts are therefore quite costly, particularly as they are used in relatively larger numbers in such installations. Principally due to the electric load, the service lives of such anode contact are relatively small and the connecting places, principally soldered (brazed) or welded connections, between the platinum and the contact carrier are also reached and attacked by the electrolyte.

It is the aim of the present invention to provide anode contacts anodes which are able to withstand better the electrical and mechanical loads, enable longer service lives and utilize more inexpensive contact materials.

The underlying problems are solved according to the present invention in that the contact body of the anode contact consists of tungsten and in that this contact body is connected by friction welding with the contact carrier made from a conventional copper-chrome alloy.

in the course of extensive tests, various contact materials were examined for their mechanical and electrical wear characteristics, primarily as regards welding together, consumption and material flow. Tungsten was thereby determined to be the most suitable contact material. In comparison to platinum, more contact troubles, for example, welding together, result with tungsten at low frequencies, i.e., with a small number of cycles. However, with an increasing frequency or number of cycles, the number of contact troubles is about equally large with these two materials. With a further increase in the frequencies or numbers of cycles, the conditions, however, reverse so that with large numbers of cycles, or high frequencies, considerably fewer contact troubles occur with tungsten as the contact material than with platinum.

With platinum a surface destruction occurs due to the welding together action as well as a fine and a coarse migration or flow occur due to the arc formation. The destruction of the contact surface with tungsten is caused exclusively by material-flow or migration. The material build-up and structure at the contact surfaces which leads to the troubles, therefore results considerably slower with tungsten.

A further cause for the contact troubles is the inference of hardness and density of the workpiece to be treated. Whereas platinum exhibits a relatively high susceptibility to trouble compared to Wolfram with the usual materials having a hardness of about 50 kp/mm and thereabove, the conditions reverse only with an increasing workpiece hardness. With respect to the tendency of welding together, platinum is dependent on the hardness of the workpiece whereas tungsten is not influenced thereby. A significant factor for the service life is the connection between contact carrier and contact body which is traversed by the current. It is possible with the aid of conventional friction welding to manufacture contact anodes from this material combination of the present invention, in which the service life of the connection lies above that of the contact material.

ln anode contacts with platinum, it has been discovered that the electrolyte sometimes reached between the platinum and the insulating layer up to the connection between the platinum and the contact carrier and attacked the same. In order to prevent this, provision is made according to the present invention that the contact body and/or contact carrier is provided at least at the places corresponding to the end of the insulating jacket or casing with grooves extending over the circumference into which engages the jacket or casing.

Accordingly, it is an object of the present invention to provide an apparatus for the electrochemical deburring of workpieces which avoids by simple means the aforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in an apparatus for electrochemically deburring workpieces which avoids the need for expensive materials at the contact surface, yet improves the overall service life of the anode contacts thereof.

A further object of the present invention resides in a contact anode for use in installations for the electrochemical deburring of workpieces which have a greater length of life and is substantially less prone to trouble in operation.

Still a further object ofthe present. invention resides in an anode contact of the type described above which is more fully protected against attack by the electrolyte yet utilizes considerably more inexpensive materials.

These and further objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, one embodiment in accordance with the present invention, and wherein:

The single FIGURE is a cross-sectional view through a contact anode according to the present invention.

Referring now to the single FIGURE of the drawing, reference numeral 1 designates therein a contact carrier which is made of a conventional copper-chrome alloy. A contact body 3 made of tungsten is connected with the contact carrier 1 by a friction welded connection 2. Both the contact carrier 1 and the contact body 3 are provided with grooves 4, into which engage the insulating-casing or jacket 5 made of casting resin of conventional type, such as, conventional synthetic resinous casting material. These grooves 4 at the contact carrier I serve for the better connection between the contact carrier l and the insulating casing 5 whereas these grooves 4 at the contact body 3 prevent the electrolyte from reaching the connection 2 between the contact body 3 and the contact carrier 1. At the upper end the contact carrier 1 is constructed as threaded ular to the axis, serves as abutment surface for a coil spring (not shown), by means of which the anode contact is pressed against the workpiece (not shown).

A typical example of a copper-chrome alloy for use with thecontact carrier 1 is the alloy sold commercially under the tradename Elmedur X which contains about 0.5 to about 1% by weight of chrome and about 0.05% by weight zirconium, the remainder essentially copper. However, every other copper-chrome alloy may be used with the contact carrier 1 as known to those skilled in the art.-

A typical example for the synthetic resinous casting material of the jacket or casing 5 is Bussolit gefullt (fi]led) though every other appropriate casting resin as known to those skilled in the art, such as epoxy resins and acrylic resins, may also be used.

While we have shown and described one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and we therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are obvious to one of ordinary skillin the art.

What we claim is:

1. In a device'for the electrochemical tially of tungsten for providing said contact surface and a contact carrier means frictionally welded to said contact body means and made of a metal consisting of a copper-chrome alloy, and said insulating material forms a casing forthe contact body means and the contact carrier means, at least one of said contact body deburring of workpieces that are to be connected as anodes which means and said contact carrier means being provided with circumferentially ext-ending grooves at'least at places corresponding to an end ofthe insulating casing adjacent to anend of the anode contact means, said casing engaging in said grooves.

2. A device according to'claim 1, characterized in that said grooves are provided in places of the contact body means corresponding to the end of the insulating casing.

3. A device according to claim 2, characterized in that said. grooves are provided in the contact body means below said contact carrier means to prevent the electrolyte from reaching the connection between contact body means and contact carrier means.

4. A device according to claim 3, characterized in that said grooves are provided in the contact carrier means above said contact body means for anchoring the casing.

5. In an electrode contact device forfeeding current to a workpiece to be electrochemically deburred, which comprises a contact carrier meansadapted to be connected to a power source and made of a metal consisting essentially of a copper-chrome alloy, a contact body means connected to said contact carrier means, said contact carrier means being made of a metal consisting essentially of tungsten, and an insulating casing substantially completely enclosing said carrier means and said body means except at anelec'trical feed connection of the former and a contact area of the latter the improvement which comprises said contact body means being connected to said contact carrier means by a friction weld, and said contact body means being provided with a plurality of circumferentially extending grooves at least at places adjacent to the contact area and said casing engaging in said grooves and in portions of said contact'body means between said grooves.

6. A. device according to claim 5, characterized in that the contact carrier means is provided with a plurality of circumferentially extending grooves at least in places corresponding to the end of the insulating casing, adjacent to said electrical feed connection, and said casing engaging in said grooves and those portions of the contact carrier means between said grooves.

7. A device according to claim 5, characterized in that said insulating casing is made of a material consisting essentially of casting resin. 

1. In a device for the electrochemical deburring of workpieces that are to be connected as anodes which includes a shaped tool electrode serving as cathode and adapted to contain an electrolyte flowing between anode and cathode, wherein the supply of energy to the workpiece takes place via an anode contact means surrounded with an insulating material except for an electrical current cable connection at one end and a contact surface at the other end, the improvement which comprises said anode contact means including a contact body means made of a metal consisting essentially of tungsten for providing said contact surface and a contact carrier means frictionally welded to said contact body means and made of a metal consisting of a copper-chrome alloy, and said insulating material forms a casing for the contact body means and the contact carrier means, at least one of said contact body means and said contact carrier means being provided with circumferentially extending grooves at least at places corresponding to an end of the insulating casing adjacent to an end of the anode contact means, said casing engaging in said grooves.
 2. A device according to claim 1, characterized in that said grooves are provided in places of the contact body means corresponding to the end of the insulating casing.
 3. A device according to claim 2, characterized in that said grooves are provided in the contact body means below said contact carrier means to prevent the electrolyte from reaching the connection between contact body means and contact carrier means.
 4. A device according to claim 3, characterized in that said grooves are provided in the contact carrier means above said contact body means for anchoring the casing.
 5. In an electrode contact device for feeding current to a workpiece to be electrochemically deburred, which comprises a contact carrier means adapted to be connected to a power source and made of a metal consisting essentially of a copper-chrome alloy, a contact body means connected to said contact carrier means, said contact carrier means being made of a metal consisting essentially of tungsten, and an insulating casing substantially completely enclosing said carrier means and said body means except at an electrical feed connection of the former and a contact area of the latter the improvement which comprises said contact body means being connected to said contact carrier means by a friction weld, and said contact body meaNs being provided with a plurality of circumferentially extending grooves at least at places adjacent to the contact area and said casing engaging in said grooves and in portions of said contact body means between said grooves.
 6. A device according to claim 5, characterized in that the contact carrier means is provided with a plurality of circumferentially extending grooves at least in places corresponding to the end of the insulating casing, adjacent to said electrical feed connection, and said casing engaging in said grooves and those portions of the contact carrier means between said grooves.
 7. A device according to claim 5, characterized in that said insulating casing is made of a material consisting essentially of casting resin. 